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Don’t fall into a bacteria trap

Dan Wild, Conex Bänninger business unit director UK&I, puts the case for copper over plastic when it comes to traps and waste fittings

Dan Wild, Conex Bänninger business unit director UK&I

It is said that familiarity breeds contempt and there are things we use every day that it’s all too easy to take for granted.

In this case I’m talking about the humble wash basin or sink. There are literally millions of them in homes, offices and major public buildings across the UK.

Whether it’s washing hands or washing up cups for the next coffee round, it’s tempting to think the cleansing regime ends when the water disappears down the plug hole. But just millimetres below, in the waste trap, there is still the potential for germs to linger.

The waste trap, of course, has an important function; to create a water seal in the pipework to isolate the sink from the drainage system, thereby preventing unpleasant smells and harmful bacteria from entering the building.

But in these days of heightened hygiene awareness, it is a reasonable question to ask what is the additional anti-microbial benefit of copper waste traps, when compared to plastic, and why is it not being taken advantage of?

This is particularly pertinent for healthcare settings such as hospitals and care homes. But it could equally be a consideration for educational establishments such as schools, colleges and universities, and also for offices and even factories.

Breeding ground

Copper waste traps are quick and easy to fit and, as a compression fitting, require no specialist tooling to install. And who hasn’t, at some point, had to unscrew a ‘P’, ‘S’ or bottle trap to find the inside of the plastic tubing coated in all manner of unpleasant gunge?

This bio film could be a breeding ground for the growth of dangerous bacteria, including legionella, particularly if it is a little-used sink and the water in the trap has remained stagnant.

This could be an issue during times of lockdown where, for example, office workers are encouraged to work from home for extended periods, or hotels and restaurants that are temporarily closed, and the normal regular, daily flushing of systems is not taking place.

Many studies have shown copper has a proven and quite unique water chemistry that reduces the threat of waterborne bacteria, not just legionella but also Polio virus and E-coli O157.

It has also been demonstrated that copper plumbing inhibits the growth of pseudomonas fluorescens, bacillus subtilis and bacteriophage MS2, which can cause gastrointestinal disturbance.

In healthcare establishments the management of legionella is addressed by the Department of Health’s Health Technical Memorandum, HTM04. This guidance calls for strict flushing regimes in order to minimise the risk of stagnant water in pipework.

Controlling bacteria

Hospitals must also ensure that temperatures at taps and ‘sentinel’ outlets are regularly checked and the results recorded, to show that water is consistently reaching 50°C .

This is done in order to control the growth of the legionella bacteria, which can breed in stagnant water between 25°C and 45°C, doubling every eight hours. Good design of a network fundamentally relies on keeping ‘hot water hot’ (>50°C) and ‘cold water cold’ (<20°C).

Along with being anti-microbial, copper also performs well in terms of its linear thermal expansion – or lack of it. Where the temperature rises by 30°C, copper pipework will expand by just 5mm over 10 metres.

While marginally bettered by steel (4mm), it matches stainless steel, is better than aluminium (7mm) and comprehensively outperforms PE (Polyethylene) (54mm) and PVC (60mm).

Copper is also a sustainable material of choice as it is 100% recyclable. In fact, some 80% of copper ever mined is still in use today.

While it takes 100 gigajoules of energy to refine one ton of copper, it takes only 10 gigajoules to reprocess it. So, recycling is 90% better when environmental costs are taken into consideration.

In these days when there is a greater emphasis on more eco-friendly solutions, there is a strong argument for installers and contracting companies to choose a material such as copper with its ‘green’ credentials.

And for designers, when it comes to specifying a system, or commissioning a retrofit, they should take into account that materials and components can contribute to unwanted bio film growth. But by choosing copper wastes and traps they can harness its anti-microbial properties to combat that risk.

3 February 2021

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